The present invention relates to a method of making surfaces of processed products smooth, and particularly to a method of making surfaces of semiconductor devices smooth by filling concavities of uneven surfaces of semiconductor devices with an insulating film material.
Abrasive techniques have been so far used for processing the surface of optical glass. In the field of semiconductor devices, abrasive techniques have been used to make the surface of substrate become mirror finished. According to recent techniques, when the surface of interlayer insulators in the process of forming a multilayer interconnection is made smooth, abrasive techniques are applied to make the surface of the substrate smooth after a buried insulating film is formed in the trench isolation. In the isolation process, in particular, since the size of a device isolation region that can be realized by a prior-art selection oxide film is limited, the trench isolation using abrasive techniques has been indispensable for the planarization process of the surface of the semiconductor devices.
As a method of forming a trench isolation using an abrasive technique for making the surface of a semiconductor device smooth, there has been proposed a method (see JP-A-6-295908, laid-open on Oct. 21, 1994) in which a first stopper layer is formed on the surface of convex portions of a semiconductor substrate having concavities and convexities on its surface, a buried insulating film is deposited on the concavities of the surface of the substrate, a second stopper layer is selectively formed on the surface of the concavities of the buried insulating film and the above-mentioned buried insulating film is removed until the surface of the first stopper layer is exposed by the planarization abrasive technique.
Also, in order to make the surface of the substrate become smoother, there are known techniques disclosed in JP-A-7-263537, laid-open on Oct. 13, 1995, and JP-A-8-8218, laid-open on Jan. 12, 1996.